At a recent Senate Appropriations subcommittee hearing on the fiscal 2016 budget, Leahy held up a jug of genuine Vermont maple syrup from Butternut Mountain Farm of Morrisville and then a store-brand box of Maple & Brown Sugar Instant Oatmeal, which he said contains "no maple whatsoever."

He asked Hamburg, a witness at the hearing, if FDA has enough money to "go after" the companies behind such mislabeling.

"Unless there is really strong action against some of these people, you're going to destroy something that's not only part of the culture of our state but is a very important industry in our state and one where some very, very hard-working people, through no fault of their own, are wiped out," he said.

Hamburg said FDA is aware of the issue but is challenged by the broad range of its responsibilities. The agency monitors the marketplace and does inspections, but also must rely on reports from consumers when problems occur.

"Certainly the issues around being able to pursue all of the misleading and false claims has been one that has been challenging for us in areas that range from food products to drugs to dietary supplements to cosmetics," she said.

She noted that FDA took enforcement action recently in a 2012 case in which a Rhode Island man ultimately pleaded guilty in U.S. district court in Rutland, Vt., to introducing adulterated food into interstate commerce with the intent to defraud or mislead. The case came to authorities' attention after a Vermont resident noticed that a product the man was selling online was misrepresented as pure Vermont maple syrup.